Peristaltic pump systems are commonly utilized in medical applications. For instance, such pumps are often employed during cardiovascular surgery to facilitate circulation of blood between a patient and a heart-lung machine. Other common medical uses are the transfer of blood between a patient and a kidney dialyzer, and intravenous feeding of IV solutions.
Peristaltic pump systems are relatively simple in construction typically consisting of a housing having rollers which progressively compress a flexible tube at spaced intervals against an arcuate surface or raceway so as to flatten or locally reduce the cross-sectional area of the tube. As the rollers continue to roll over the tube, the successive flattened portions expand or return to the original cross-sectional area due to the resilience of the tube which generates a subatmospheric pressure in the tube to draw the fluid therein.
The efficiency of the pump depends on the flexing characteristics of the tube. A tube which completely seals at the flattened cross-sectional area prevents reverse flow of fluid and reflux of air to establish a volumetric pump whereby the rate of flow of fluid ca be accurately calculated by the rotational speed of the rollers. Commercially available peristaltic pump tubes are uniformly cylindrical with a uniform wall thickness and provide a fast recovery rate of the flattened portion to the normal cross-sectional area, however, the shape of the tube produces voids or cavities during expansion and the resiliency of the tube may cause excessive subatmospheric pressures to be created which may draw air into the pump system, or cause damage to the blood and other tissues, which is objectionable.
A variety of tubes incorporating various geometric configurations have been provided in an attempt to provide a more efficient pumping system with relatively little success. For instance, in U.S. Pat. No. 4,131,399 longitudinally extending internal notches or external ridges are provided to prevent the tube from completely occluding which renders the tube useless for many applications and will produce variable vacuum conditions.
U.S Pat. Nos. 2,406,485 and 3,192,863 incorporate tubes having configurations which reinforce the tube and permit the tube to completely occlude as the rollers pass thereover. However, in U.S. Pat. No. 2,406,485 the tube is provided with an internal notch and a reinforcing external ridge which produces an increased wall thickness and the hose requires special adapters for connecting the tube to standard extracorporeal devices since the tube is not of a circular cross-sectional shape. Also, stretching of the tube, requiring special tools, is necessary during installation which is an inconvenience and is time consuming for the operator. Similarly, the tube in U.S. Pat. No. 3,192,863 incorporates a special configuration including a longitudinally extending fin projecting therefrom which requires additional material to form the tube and a complicated raceway construction for receiving and supporting the same.
It is an object of the invention to provide a tube for peristaltic pumps wherein the tube incorporates a simple construction for optimizing and controlling the flexing characteristics of the tube.
Another object of the invention is to provide a tube for peristaltic pumps wherein the tube is provided with a pair of longitudinally extending notches or grooves defined in the exterior surface thereof for improved control and flexing characteristics and permitting the tube to completely seal with a minimum of strain imparted to the tube.
A further object of the invention is to provide a tube of a generally circular cross-section for peristaltic pump systems wherein the tube incorporates longitudinally extending notches or grooves defined in the exterior surface thereof whereby the depth of the notches and the durometer of the tube may be selected to control the flexing characteristics of the tube and generate the desired negative pressures for a particular application.
A further object of the invention is to provide a tube which is safe for medical applications as excessive negative pressure at the cannulation site is prevented.
Still a further object of the invention is to provide a tube incorporating a pair of external notches or grooves formed by removing material at the areas which would otherwise undergo the greatest strain during compression to prevent the tube from cracking and bursting over extended periods of usage.
Another object of the invention is to provide a tube for peristaltic pump systems wherein the tube incorporates a simple low cost construction which is easily and quickly installed in conventional peristaltic pumps without requiring stretching or special tools.
The tube of the invention is adapted for use in peristaltic pump systems wherein fluid is transferred through the tube by the action of rollers progressively compressing the tube at spaced intervals against an arcuate raceway having an axis common to that about which the rollers rotate. The tube includes an inlet end, an outlet end, and an internal passage extending therebetween. Exteriorly, the tube is provided with a pair of longitudinally extending oppositely disposed notches or grooves defined in the exterior surface thereof.
The notches or grooves are located at the areas of the tube which would otherwise undergo the greatest strain when the tube is compressed, to provide improved flexing characteristics and permit the tube to completely occlude at the locally flattened cross-sectional areas. The geometric configuration and depth of the notches and the durometer of the tube may be selected to optimize the flexing characteristics of the tube during return of the tube to its normal shape to generate the desired negative pressures for a particular application. Because the tube completely occludes, a volumetric pump is established, and no leak passages are created for return or reverse flow of fluid or reflux of air.
The tube is less susceptible to cracking and bursting over extended periods of usage as the material which normally would have undergone the greatest strain has been removed to form the notches. Because the notches are formed exteriorly, the interior of the tube maintains a substantially circular cross-section for easily and conveniently connecting the inlet and outlet ends to standard extracorporeal devices. The simple construction of the tube provides improved efficiency in peristaltic pumps while a low cost construction is maintained.